Brachial plexus may be located in different ways,
including paresthesia, transarterial puncture, loss of nervous sheath resistance
and neurostimulation. Axillary route has been indicated for forearm, arm and
hand procedures 1-3. The multiple stimulation technique during axillary
block, in which each nerve is located with stimulator and injections are performed
separately, provides high success rates and decreases installation time 4-7.

The axilla is a region at low risk of vital structures
damage, being the axillary artery an excellent guide for axillary block. The
transarterial technique is performed by injecting local anesthetics in two different
areas separated by the axillary artery and has low incidence of failures1,5.
Neurostimulation allows the easy identification of each of the four possible
motor responses: median, ulnar and radial nerves stimulated within the nervous
sheath, and musculocutaneous nerve in the upper axilla or close to coracobrachial
muscle. This way, neurostimulation allows for fractional and directed local
anesthetic injection and, differently from paresthesia search with a needle,
has a low probability of direct nervous trauma.

Several studies on individualized brachial plexus
block have shown that upper limb anesthetic extension and depth were better
with location and blockade of the 4 terminal branches, notwithstanding the longer
time for the procedure, which would be balanced by faster onset 4-8.

This prospective study aimed at comparing onset,
duration, effectiveness and failures of brachial plexus block induced with two
techniques to identify the presence of the needle in the axillary perivascular
compartment: multiple stimulation and transarterial perivascular injection.

METHODS

After the Publication and Disclosure Board of
Directors approval, participated in this prospective study 70 patients aged
20 to 60 years, physical status ASA I and II, submitted to orthopedic forearm
and hand surgeries who were randomly distributed in two groups (group MNS =
40 patients and group TA = 30 patients) according to the technique. All patients
gave their informed consent after being informed in detail about the technique.

Patients were not premedicated. After venoclysis
with 18G or 20G catheter, lactated Ringer's solution was slowly injected.
Monitoring in the operating room consisted of continuous ECG at CM5, noninvasive
blood pressure and pulse oximetry. The patients received 50 to 100 µg intravenous
fentanyl associated to 10 mg metochlopramide and were only sedated with midazolam
after blockade installation and beginning of surgery.

Multiple Stimulation Technique (MNS)

Patients were placed in the supine position with
90º arm abduction and forearm extended or flexed. Axillary artery was drawn
in the biceps muscle sulcus, on the line connecting the umeral insertion of
pectoral and greater dorsal muscles. A point was marked 3 cm below this, were
infiltration was performed anterior and posterior to the artery for the entry
of the needle connected to the stimulator.

After a skin wheal raised on the marked point,
a B. Braun 22G 0.70 x 50 mm electrically isolated needle was connected to a
peripheral nerve stimulator (Stimuplex®R, B. Braun Melsungen
AG) adjusted to release a pulsatile square 1 mA current with intensity decreased
to 0.5 mA and inserted in 30º angle with the skin posterior to the axillary
artery. We tried to stimulate the ulnar nerve with responses of thenar and hypothenar
eminence muscles and clamping of fifth finger and thumb, or the radial nerve
with hand extension.

Recently prepared 20 mL of 1.6% lidocaine with
1:200,000 epinephrine were injected. Needle was then removed and reinserted
anterior to the axillary artery, in an attempt to stimulate the median nerve
and obtain muscle contractions of anterior forearm and hand flexion. At this
point, additional 20 mL of the prepared solution were injected. After, needle
was removed from the axillary bundle and musculocutaneous nerve was looked for
by orienting the needle toward the coracoid apophysis at the insertion of the
coracobrachial muscle. When biceps contraction and flexion of the forearm over
the arm were reached, 10 mL of the prepared solution were injected.

Five randomly selected patients received 1 mL
iohexol contrast (300 mg.mL-1) in each nerve before anesthetic injection
for radiological evaluation.

Transarterial Technique (TA)

Patients were placed in the supine position with
90º arm abduction, flexed elbow and hand under the head. Axillary artery
was palpated and marked. A 30 x 8 needle perpendicular to the artery was slowly
introduced until blood reflux was obtained, when it was introduced slightly
beyond until artery transfixation, confirmed by the lack of reflux. At this
moment, recently prepared 30 mL of 1.6% lidocaine with 1:200000 epinephrine
were slowly injected observing possible signs of vascular injection. Needle
was then slowly backed, going once more through the artery lumen and being positioned
anterior to it, when remaining 20 mL of the solution were injected. Needle was
then removed and arm was positioned along the body with axillary compression.
Five randomly selected patients received 1 mL iohexol contrast (300 mg.mL-1)
in each side of the artery before anesthetic injection for radiological evaluation.

Analgesia was evaluated in both groups by skin
clamping and observing patients' pain manifestations, aiming at determining
the extension of sensory block of musculocutaneous nerve in forearm radial border,
radial nerve in dorsal face of hand, ulnar nerve in medial hand and fifth finger,
and median nerve in the palm. The following parameters were evaluated: 1) anesthetic
onset: time elapsed from beginning of puncture to loss of sensitivity in the
four nerves; 2) sensory block duration: time elapsed between beginning of puncture
and total sensory recovery; 3) motor block duration: time elapsed between beginning
of puncture and total recovery of blocked limb; 4) tourniquet perception; and
5) complications and side effects.

Blockade was considered complete if all nerves
were blocked with the preconized volume. If there was need for additional injection
or anesthetic complementation, blockade was considered incomplete. In this case,
additional anesthetic dose would only involve the nerve of the unblocked area.
Blockade failure was defined as the need for general anesthesia.

Tenoxicam (40 mg) and dipirone (30 mg.kg-1)
in 100 mL lactated Ringer's were administered at surgery completion and
patients were transferred to the ward. All patients were followed up for 48
hours via telephone to check for complications on blockade site. If there were
any signs, patient should return to the hospital to be evaluated by the authors.
All patients were asked about their satisfaction with the technique.

Results were evaluated by t test with
Welch correction for levels of freedom and by Fisher's exact test to compare
two percentages, considering significant p < 0.05.

RESULTS

Continuous variables results are shown as mean
± standard deviation. Distribution by age, weight,
height and gender is shown in table I;
sensory and motor block onset and duration are shown in table
II. Contrasted study of each nerve with the multiple stimulation technique
is shown in figure 1, figure
2 and figure 3, and with the transarterial
technique in figure 4 and figure
5.

Mean onset has been significantly shorter for
the TA group. There has been no arterial or venous puncture with multiple stimulation
technique.

Only two patients, both from the TA group, needed
general anesthesia; remaining patients were operated with blockades. Artery
was transfixed and anesthetic solution was deposited posterior and anterior
to it in all TA group patients. Muscle contraction in the territories innervated
by median, radial or ulnar and musculocutaneous nerves was obtained in all MNS
group patients and in three TA group patients. Musculocutaneous nerve was significantly
easier to be blocked with the aid of nerve stimulator (p = 0.034) (Table
III).

Sensory and motor block duration was significantly
longer for the MNS group as compared to the TA group.

Mean lidocaine dose was 13.5 mg.kg-1
for the MNS group being 16.6 mg.kg-1 the highest dose. Mean dose
was 12.5 mg.kg-1 for the TA group, with maximum dose of 15.09 mg.kg-1.
There has been no clinical signs of systemic local anesthetic toxicity in both
groups.

No patient has referred pain at surgery site.
However, four patients have referred tourniquet pain, being two from the TA
group and two from the MNS group, without significant difference.

There were no nervous injuries in the MNS group
or hematoma or anesthetic vascular injection in the TA group.

DISCUSSION

When several lidocaine plus epinephrine injections
are axillary applied in the brachial plexus, the use of plexus stimulator (3
injections) results in a similar success rate to the transarterial technique
(2 injections), however demanding longer time for surgery beginning. Several
authors consider axillary block success when analgesia is present in all surgical
areas. This definition is clinically similar success rates sufficient, but implies
a false success rate as compared to different blockade techniques 5.
We have considered the blockade complete when all forearm nerves were blocked
with the first injection. Complementation was needed in three MNS group patients
in different nerves: musculocutaneous, radial and ulnar. Complementation was
needed in three TA group patients and blockade failure was seen in two other
patients of this same group.

The brachial plexus block requires continuous
concern with the injected volume. The ratio between injected anesthetic volume
and extension of analgesia was firstly described in 1961 9. Although
mean axillary neurovascular compartment volume is just 42 mL 9, single
60 to 80 mL perivascular injection may result in partial block 10,11.
This was initially explained by insufficient proximal anesthetic spread to nervous
branches and upper plexus divisions caused by the umeral head, but was not confirmed
by the randomized controlled studies 12,13.

The two axillary block techniques improve anesthetic
spread in the neurovascular sheath, as compared to single injection techniques:
the transarterial with two injections and the multiple nerve stimulation with
three or four injections. The transarterial technique with 800 mg of 1.6% lidocaine
with epinephrine has resulted in 95% to 100% success rate without any adverse
effect 1.

Anatomic studies have shown that musculocutaneous
and axillary nerves leave neurovascular sheath at the coracoid process, in line
with the fact that 50 mL of 1.6% lidocaine have not blocked the musculocutaneous
nerve in three patients of this series. There are few studies on the multiple
stimulation technique with nerve stimulator. A comparison of three axillary
block techniques (catheter, paresthesia and nervous stimulation) has shown higher
success rate when more than one nerve is stimulated (50% for 1, 80% for 2 and
100% for 3 nervous stimulations) 14. Three stimulations technique,
where only median, radial and ulnar nerves are located, has just 50% success
rate 15. Our study has included isolated stimulation of musculocutaneous
nerve, resulting in 92.5% success rate.

When anesthetic solution was injected close to
2 or 4 identified nerves, only 1 out of 15 patients needed complementation 15.
The comparison between single injection and injection after locating 3 nerves
has resulted in 43% effectiveness versus 90%, respectively 4. It
has been recently shown that double stimulation results in 92% success rate
while single injection results in just 52% 16. Our study comparing
triple injection after locating three nerves with the neurostimulator and the
transarterial technique with two injections has resulted in 92.5% success rate
with triple injection as compared to 83.3% with double injection.

Success rate depends on surgery site and blockade
extension 17 thus being hard to compare it among different studies.
We were more concerned with analgesia spread than with motor block for surgical
success. Initially we have not looked for the nerve innervating the surgical
site, but rather for stimulation internal and external to the axillary artery.
Median nerve is usually easier to be located with nerve stimulator and its investigation
has become popular for the single injection method 17.

Incomplete musculocutaneous nerve blockade is
a common axillary technique problem because it is not close to the axillary
artery 18. In our study, double injection with the transarterial
technique and the attempt to stimulate this nerve with the three stimulations
technique has shown that this problem may be minimized with the latter approach.

Transarterial access is achieved with double
injection, being one superficial and the other deep to the axillary artery.
Success rate of 83.3% in our study was close to that observed in some studies
(79% 19, 88.8% 20), however lower than 92% 16
and 95% 1 of other studies. Success rate of 92.5% obtained with multiple
stimulations is similar to results obtained by other studies, which have varied
from 88% to 93% 4,5,8.

Notwithstanding the increased risk of complications
such as vasospasm, hematoma and/or pseudoaneurysm 21,22, transarterial
is considered a safe technique, shown by a prospective analysis of 1000 patients
20. In our study, 48 hours follow up has not evidenced any complication.
Major concern during multiple stimulation location is the possibility of puncture-induced
neuropraxis. This possibility was minimized in our study by the nerve stimulator
and by slow needle advance while current was decreased to 0.5 mA. In addition,
analgesic complementation was never injected in the same site of the previous
injection.

Maximum lidocaine plus epinephrine dose recommended
for regional anesthesia in adults is 7 mg.kg-123. However,
when lidocaine is diluted for infiltrative anesthesia, dose varies from 45 mg.kg-1
in slim patients to 50 mg.kg-1 in obese patients 24. Lidocaine
dose to obtain 5 µg.mL-1 plasma concentration varies according
to the administration site 25.

There have been no signs of intoxication in 346
patients receiving 900 mg lidocaine with epinephrine (30 mL of 2% and 30 mL
at 1%) for transarterial brachial plexus block and success rate has been 100%
26. A different study has found mean plasma concentration of 2.9
µg.mL-1 after transarterial brachial plexus block with 900 mg
lidocaine, with highest individual value of 5.6 µg.mL-1 representing
a dose of 18 mg.kg-1

In this series, there has been no anxiety related
to multiple injections technique because the method has been thoroughly explained,
needle pathway has been anesthetized, stimulation was achieved with 0.5 to 1
mA and fentanyl has been previously administered.

In conclusion, when axillary brachial plexus
block is achieved with the aid of peripheral nerve stimulator and when the musculocutaneous
nerve is stimulated together with radial and/or median and/or ulnar nerve, the
result is similar to double injection transarterial technique, but with more
effective musculocutaneous nerve block. However, time to surgery beginning is
longer with the use of neurostimulation.

Transarterial dose of 900 mg routinely used in
more than 500 patients 27 is 12.5% higher than 800 mg used in this
study. Highest dose has been 16.6 mg.kg-1, lower than 18 mg.kg-1
used in the above-mentioned study 27. Similarly, there have been
no clinical manifestations of systemic toxicity with lidocaine plus epinephrine.